The present invention relates to implantable medical devices. In particular, the present invention relates to the simulation and testing of magnetic field induced vibrations in implantable medical devices.
In a magnetic resonance imaging (MRI) scanner, a magnet creates a strong magnetic field that aligns the protons of hydrogen atoms in the body. The MRI scanner then exposes the protons to radio frequency (RF) energy, which spins the various protons to produce a faint signal that is detected and subsequently rendered into an image. During this process, a static magnetic field and a time-varying gradient magnetic field are produced. These fields may result in mechanical interactions between an implantable medical device (IMD) and the MRI environment. In particular, interactions between the static magnetic field and the gradient magnetic field produce vibrations in the IMD. The vibration response of the IMD depends on the frequency and magnitude of the gradient magnetic field. The magnitude of the gradient magnetic field varies with position in the MRI scanner.
As MRI scanner technology evolves, the rate of change of the gradient magnetic field will increase to produce more detailed scans of human tissue. As the slew rate of the gradient magnetic field increases, the intensity of the vibration response of the IMD will also increase. Thus, it is important to test the reliability of IMDs in field strengths and slew rates beyond those produced by contemporary clinical MRI scanners to assure that IMDs perform reliably in future generations of clinical MRI scanners.